I have really found it annoying the way the frames flop around until the second row of panels are stitched in place. I have tried using cans and boxes to hold them up with limited success.On my latest build I had a bit of scrap 4x2 lumber hanging around. I cut off some short lengths about 5 or 6 inches long. I laid one on its side on the hull, butted up against each frame. Then I pushed a thumb tack through the frame into the end of the block of wood. Everything was held securely in place. Simple and easy.

When I stitched the second of my 2 Wadefish together I did it under my mezzanine floor in my shed & set up a series of wire loops from the beams down under the panels & back up the other side to the beam again.

This stopped them from flopping about & also roughly held them in the right shape